1Z0-811 Java Class Design 2

Question 1

Which keyword prevents a class from being subclassed in Java?

Accepted Answer

final

Answer

The `final` keyword on a class declaration prevents any other class from extending it.

Question 2

What is the result of calling a non-static method on a null reference in Java?

Accepted Answer

NullPointerException at runtime

Answer

Invoking an instance method on a null reference throws NullPointerException at runtime.

Question 3

Which access modifier makes a member accessible only within its own class?

Accepted Answer

private

Answer

`private` restricts visibility strictly to the declaring class itself.

Question 4

Given `class B extends A`, and both define `void print()`, what determines which `print()` runs when called via an `A` reference holding a `B` object?

Accepted Answer

The object type (B) — runtime polymorphism

Answer

Java uses dynamic dispatch: the actual object type (B) determines which overridden method executes at runtime.

Question 5

What is the purpose of the `super()` call inside a constructor?

Accepted Answer

To call the parent class constructor

Answer

`super()` explicitly calls the parent class's constructor and must be the first statement in the child constructor.

(1Z0-811) Oracle Java SE11 Programmer Practice Test

(1Z0-811) Oracle Java SE11 Programmer Practice Test

1Z0-811 Java Class Design 2